Opened 4 years ago

Closed 4 years ago

Last modified 21 months ago

#12377 closed defect (fixed)

XO-4 B1 timeout entering DCON mode

Reported by: Quozl Owned by: Quozl
Priority: low Milestone:
Component: ofw - open firmware Version: Development firmware
Keywords: Cc:
Blocked By: Blocking:
Deployments affected: Action Needed: no action
Verified: no


A long duration DCON freeze and unfreeze test was set up, consisting of:

dev /display
: hdd-led-off  led-storage-gpio# gpio-clr  ;
: hdd-led-on  led-storage-gpio# gpio-set  ;
: yy  hdd-led-on dcon-freeze hdd-led-off dcon-unfreeze  ;
: xx  begin yy key? until key drop  ;
gvsr xx gvsb xx

On XO-4 B1 SKU292 (4b18) with Q7B08.

About 3900 seconds into the test, a scrolling error began:

Timeout entering DCON mode

Interrupting the test, diagnosis showed:

  • get-msecs returned 3baf52,
  • dcon-freeze was generating the error,
  • dcon-unfreeze was not generating any error,
  • has-dcon-ram? returned true,
  • brightness keyboard keys continued to work properly,
  • mode@ returned 69 (pass-through disable, backlight enable, color swizzling enable, color anti-aliasing enable),
  • select /dcon dcon-unload or dcon-load had no effect on screen image, it continued to be live,
  • the alternate function register for GPIO 142 was correct (1), and the GPIO direction was correct (output), and gpio-pin@ 1 and tracked dcon-unload (1) and dcon-load (0),
  • a soft reset of the DCON memory controller was ineffective, (1 42 dcon! 1 ms 0 42 dcon! ),
  • a system power cycle cleared the problem.

The problem has not reproduced on two other units (SKU293, SKU294).

Change History (6)

comment:1 Changed 4 years ago by Quozl

  • Action Needed changed from reproduce to diagnose

Reproducible on all three units here when I returned from lunch.

comment:2 Changed 4 years ago by Quozl

"don't believe this is a new problem --- when this happens in Linux, the DCON is power cycled" -- John.

comment:3 Changed 4 years ago by Quozl

  • tested DCON power cycle, dcon-suspend dcon-resume did not clear problem, dcon-suspend d# 3 ms dcon-resume did clear problem.
  • tested disabling the default pull-ups on DCONSTAT and DCONIRQ#, no effect.
  • compared DCON register values between working and non-working states, no difference.
  • reviewed kernel driver, could not find code that would power cycle DCON for this problem,
  • did find a comment that "the DCON seems to get confused if we change DCONLOAD too frequently", which we are doing half the time in Open Firmware, but adding a 25 ms delay between each change does not prevent problem.

An additional observation about the symptom: the static screen shimmers for about ten seconds after the test-dcon-freeze-glitch is stopped by key press.

comment:4 Changed 4 years ago by Quozl

  • Action Needed changed from diagnose to add to build

Fixed in svn 3543, by power cycling the DCON whenever the timeout occurs. Tested over 40k cycles.

comment:5 Changed 4 years ago by Quozl

  • Action Needed changed from add to build to no action
  • Resolution set to fixed
  • Status changed from new to closed

Is in Q7B16.

comment:6 Changed 21 months ago by Quozl

  • Milestone 4-firmware deleted

Milestone 4-firmware deleted

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